I've had this happen rarely too, most players don't notice cause they simply think a box didnt appear.

My sister often uses my other PC next to me and I can see a box drop on my screen but not on hers or vice versa, moving out of range and back in makes it reload and show up. It also happens on npcs/maws etc on occasion, moving out of range and back makes them load as normal.

Zone is at cap of boxes, but wont display any boxes for you because there are no placeholders left.
This is wrong cause the box loads on other screen and reloads if you move out of range and back in.